32 ASTRID CLEVE, ON RECENT FRESHWATER DIATOMS. 



Var. Mconstricta Grun. — V. H. XXXIII, 19. 



The specimens from Lule Lappmark measure O, o. 5 mm. 

 in length and tlins are only half tlie length of tliat figured 

 by Grun. in V. H. 1. c. The val ve sometimes has 2 slight 

 constrictions on the dorsal margin also. Striae 9 to 11 in 

 0,01 mm. 



Kv. 32, Ks. 15, 20, S.-K. 33. — Somewhat rare. 



As seen above, the average number of striae in E. pec- 

 tinalis and its varieties is in Lule Lappmark higher than 

 that of 8 in 0,oi mm., stated by Van Heurck in the Synopsis 

 p. 142. 10 to 12 striae in 0,oi mm. is the number usually 

 occuring. 



E. media A. Cl. n. sp. - Pl. I, 38. 



Valve gently arcuate with rounded subcapitate ends, 

 0,04 5 to 0,0 6 5 mm. in length, 0,oo9 mm. in breadth. Dorsal 

 margin slightly impressed in the middle. Striae 15 to 16 in 

 0,01 mm., equidistant and of equal length. 



Nu. 14, 18. — Rare. 



The outline of this species is about the same as that of 

 E. major var. bidens in V. H. XXXIV, 15; but the size and 

 striation of these two forms being quite different, I think they 

 must be specifically distinguished. 



E. formica Ehb. — V. H. XXXIV, 1. 



Jm. 6, Ks. 15. — Rare. 



E. arens Ehb. — V. H. XXXIV, 2, 3. 



As typical I consider forms with broad. obtuse ends, and 

 10 to 13 almost equidistant striae in 0,oi mm. Valve O, o 4 

 to 0,0 6 mm. in length, 0,oo7 to 0,oo9 mm. in breadth. 



Kv. 16, 28, 32, 34, Nu. 17, 18. Km, 10, 30, Ks. 15, 20, 

 Ll. 21, Jm. 31, Tj. 42, Gl. 47, Ke. 49. — Frequent. 



Var. uiicinata Grun. — V. H. XXXIV, 13, 



Valve more slender. The lines limiting the ends con- 

 verge towards the dorsal side of the vah^e. 



^Kv. 9, Ks. 15, 20, Jm. 6, Ll. 21, Tr. 38, Nu. 41, Tj. 42, 

 Km. 30. — Moderately frequent. 



Of this variable species, a great number of different 

 forms occur in Lule Lappmark, passing into another; thus 

 no limit can be fixed between the typical form and the var. 

 minor Grun. in V. H. XXXIV, 3, for which reason I have 



